This invention relates to the use of amphiphiles for permanently improving the adhesive and/or coating compatibility of polyolefin-based moldings, fibers and films.
Molded workpieces of any three-dimensional form, including polyolefin-based moldings, fibers and films, are used on a very wide scale in practice. An important problem area here is improving the surface properties of these structurally nonpolar hydrocarbon components. Thus, the poor adhesion of coatings and adhesives is a central problem which has remained unsolved for decades despite numerous attempts to find a solution. A comprehensive account of the various proposals which have been made with a view to solving the stated problem can be found, for example, in EP 0 311 723 to which reference is made here.
It is known from the prior art that the compatibility of plastic surfaces with coatings and adhesives can be improved, for example, by oxidative after treatment processes, such as corona or plasma treatment. In processes such as these, the surface of the plastic is oxidized or chemically modified in the presence of gases and discharges, so that certain surface properties of the plastic can be modified. However, apart from their high energy consumption, processes such as these always involve an additional step and lead to ozone emissions in the manufacture of plastic parts.
In addition, chemical pretreatment processes, including for example treatment with fluorine or chlorine gas, with chromosulfuric acid or fluorosulfonic acid, etc., have also been known for some time.
EP-B-372 890 describes polyolefin- or polyester-based fibers with a lubricant adhesively applied to their surface. This lubricant comprises a mixture of (1) fatty acid diethanolamide, (2) a polyether-modified silicone, (3) a sorbitan fatty acid ester and (4) a metal salt of an alkyl sulfonate. Components (1) to (4) are present in special quantity ratios. According to page 3, lines 20 to 26, the mixture of components (1) to (4) is applied to the surface. The technique by which the mixture containing the four components is applied to the surface of fibers is described in detail on page 4, lines 6 to 9. The application techniques mentioned include a) the use of rollers, b) spraying and c) immersion. Accordingly, the process according to EP-B-372 890 is a process in which a mixture of components (1) to (4) is applied to the surface of polyolefin moldings in an additional process step. ad Accordingly, the expression "adhesively applied to the fiber surface" used in claim 1 of EP-B-372 890 may be clearly interpreted by the expert to mean that any adhesion involved is loose and temporary, for example in the form of relatively weak adhesion forces, and cannot in any way to be considered to represent permanent anchorage.
U.S. Pat. No. 5,045,387 describes the treatment of polyolefin-based fibers or films in which special polyalkoxylated polydimethyl siloxanes or alkoxylated ricinoleic acid derivatives are applied to the surface.
In view of the very widely used traditional chemical after treatment processes, such as corona and plasma treatment, it is known to the expert that no exact statements can be made as to the various processes involved. However, it has been established that oxidative surface changes occur and result in the formation of certain "active centers". However, their concentration generally decreases with time so that the pretreatment effect also is only in evidence for a certain time, generally not more than 72 hours (cf. for example, Klaus Stoeckert (Editor), "Veredein von Kunststoff-Oberflachen", Munich 1974, page 137).
One feature common to all the known processes is that, in general, the desired surface effects are only temporarily present.
EP-B-616 622 relates to extrudable compostable polymer compositions comprising an extrudable thermoplastic polymer, copolymer or mixtures thereof containing a degradation-promoting system of an auto-oxidative component and a transition metal. The auto-oxidative system comprises a fatty acid, a substituted fatty acid or derivatives or mixtures thereof, the fatty acid having 10 to 22 carbon atoms and containing at least 0.1% by weight of unsaturated compounds and at least 0.1% by weight of free acid. The transition metal is present in the composition in the form of a salt in a quantity of 5 to 500 ppm and is selected from the group consisting of cobalt, manganese, copper, cerium, vanadium and iron. In the form of a film around 100 microns thick, the composition is said to be oxidatively degradable to a brittle material over a period of 14 days at 60.degree. C. and at a relative air humidity of at least 80%.